CreatePod and MakePod only accepted an `isPrivileged` boolean, which made it
impossible to write tests using those helpers which work in a default
framework.Framework, because the default there is LevelRestricted.
The simple boolean gets replaced with admissionapi.Level. Passing
LevelRestricted does the same as calling e2epod.MixinRestrictedPodSecurity.
Instead of explicitly passing a constant to these modified helpers, most tests
get updated to pass f.NamespacePodSecurityLevel. This has the advantage
that if that level gets lowered in the future, tests only need to be updated in
one place.
In some cases, helpers taking client+namespace+timeouts parameters get replaced
with passing the Framework instance to get access to
f.NamespacePodSecurityEnforceLevel. These helpers don't need separate
parameters because in practice all they ever used where the values from the
Framework instance.
